ALBERT

Description: In order to understand the influence of surrounding catchment characteristics on the CDOM concentration different types of surface waters in the Lena river delta region were investigated regarding their geochemical composition. The Lena River Delta consists of three geomorphological main terraces that differ in their relief, hydrological and cryolithological characteristics, which possibly influences the content of dissolved substances in their associated water bodies and in the neighboring river branches. During summer seasons of 2013-2014 water samples were collected from river branches as well as from lakes and melt-water streams on the first and the third main terraces and analyzed them for concentrations of colored dissolved organic matter (CDOM), dissolved organic carbon (DOC), and main and trace elements (Na, K, Mg, Ca, HCO3, F, Cl, SO4, Fe, Si, Sr). This type of research was carried out for surface waters in the Lena delta region for the first time. Statistical analysis revealed several correlations between CDOM, DOC and mineral ions. For example, R-squared (the coefficient of determination) for CDOM and Cl and for CDOM and Na in Lena River branches were 0.52 and 0.51, respectively. Correlation between CDOM and F was also found for melt-water streams from the Ice Complex (third terrace) (R-squared = 0.5). Analysis of the relationship between CDOM and DOC showed strong correlation of these parameters for lakes (R-squared = 0.98) and lower correlation for river branches (R- squared = 0.48). In streams formed by the thawing of Ice Complex deposits on the third terrace was found the highest values of CDOM and DOC, but a correlation between them was not observed. A clear dependency was found out between CDOM and DOC correlation and the location of lakes on different terraces with specific permafrost conditions. A stronger correlation was observed for the lakes located on the third terrace (Ice Complex) compared to lakes located on the first terrace (Samoylov Island). Usually, lakes on the first terrace get flooded by river waters during spring, whereas lakes of the third terrace are not affected by river water inflow and have more stable conditions. The Lena delta branches are influenced by differing surrounding conditions, therefore CDOM and DOC concentrations change during summer season and did not show strong correlations.

Description: Nowadays due to climate change the interest to the hydrological processes in the permafrost affected regions is growing. Permafrost soil is important carbon pool and thawing can cause the increase of carbon outflow from Arctic river basins. During Russian-German expeditions Lena-2012 and 2013 some measurements were carried out on the catchment of the Fish Lake on Samoylovsky Island in the Lena River delta. Fish Lake is a thermokarstpolygonal lake, and the landscape of its catchment is typical for the Arctic polygonal tundra. These measurements were done in order to study the DOC income to the lake from an active layer of the catchment. Measurements of the DOC concentration in the pore water and the depth of seasonal thawing were made at 21 points in the 1,52 sq km catchment. The points were selected in different parts of the polygons to consider the heterogeneity of the landscape. Samples for DOC were analyzed in the field using a Spectro::lyser probe and in the lab with a Shimadzu TOC-L probe. In August the depth of the active layer was between 20 and 60 cm: 20-30 cm on the polygon rims, 30-60 cm in the polygon centers and near the lake. During the month when the measurements were made the depth increased by 10-15. For August the DOC concentration in the pore water of the active layer was 8-51 mg/l, for July – 5-30 mg/l, which correlates with the results of other researches in Arctic region. The changes in DOC concentration in pore water for the different thaw depth were examined. Maximum was observed on the depth 35-40 cm for July and 45-55 cm for August. So, for the same depth the variance in the concentration was the most significant. The DOC flux to the Fish Lake was calculated using the mean measured concentration and water runoff from the catchment (Ogorodnikova, 2011). The DOC daily flux to the lake is evaluated as about 0,8 kg per day and the flow rate is 0,5 kg/ km2*day, which is in ten time less than for the lake catchment of southern areas (Moore, 2003). Prolongation of field measurements is necessary for reasons clarifying and for better understanding of DOC flux formation processes under different conditions including thawing increase.

Description: Previous studies have shown that arctic river delta systems are areas of accumulation of geochemical substances at the sea-river mixing zone. In the Lena River Delta our previous work shows the tendencies of water runoff redistribution changes and heterogeneity of suspended supply distribution along the delta branches, accumulation and erosion zone in the different parts of the delta. Nevertheless, the processes of geochemical flow transformation in the subaerial deltas are so far underestimated. In order to close this gap, we sampled water, suspended and bottom sediments in the Lena River Delta in the summer seasons of 2010 and 2014. Most of the sampling points were tight to the profiles of hydrological measurements held in the delta and highlighted in Fedorova et al. [2015]. The results show that geochemical transformation of the Lena River runoff is taking place in the delta. The most active time for the transformation is the summer season due to the activity of sediment accumulation and biogeochemical processes. Hydrological conditions in the delta affect also its hydrogeochemical characteristics. Furcation of the delta branches affects the hydrodynamic conditions of different delta areas. The factors influencing the geochemical characteristics of the delta were identified on the base of geochemical indexes approach applied to sediments and statistical factor analysis. Based on geochemical indexes (Al/Na, Si/Al, Fe/Mn and Fe/Al ratios) similar conditions were determined for the main branch of the Lena, the upstream parts of Bykovskaya and Tumatskaya branches and in Olenekskaya branch near Chay-Tumus. Despite of high runoff the branches are characterized by element accumulation, which can be explained by decreasing of flow turbulence and specificity redox conditions in these areas. Bottom sediments are one of the most important indicators of geochemical transformation processes. The results of statistical factor analysis show three main factors for formation of the these geochemical conditions in the delta: 1. the general water flow of the Lena River, which is influenced by the lithogenous base of the river catchment, 2. the cryogenic condition of the Lena Delta (permafrost degradation processes and cryogenic weathering) and 3. biogeochemical transformation during redistribution of chemical water components , suspended matter and bottom sediments. Acknowledgements The research was supported by grant No. 14-05-00787 A of Russian Foundation for Basic Research References Fedorova, I.; Chetverova, A.; Bolshiyanov, D.; Makarov, A.; Boike, J.; Heim, B.; Morgenstern, A.; Overduin, P. P.; Wegner, C.; Kashina, V.; Eulenburg, A.; Dobrotina, E. and Sidorina, I. [2015]: Lena Delta hydrology and geochemistry: long-term hydrological data and recent field observations. Biogeosciences, 12(2):345–363, doi:10.5194/bg-12-345-2015.

Description: The Lena River delta is one of the hydrologically entertaining objects. Hundreds channels and thousands lakes as well as thawing ice complex and permafrost active layer dynamic allow to investigate spatial-temporal coherence of different scale hydrological processes. During 15 years Russian-German scientific collaboration on hydrological, hydrochemical and hydrobiological studies have been operated on different water objects for cause-effect relation of large and specific micro processes indication. Transient liquid-frozen water phase change is significant not only for active layer runoff forming but also for hydrochemical and biological specific. Thus, maximum of DOC is in the overlaying soil layer than permafrost border [Bobrova et al., 2013]. It could be used for modeling of runoff forming and biological activity estimation. Measured temperature of lacustrine bottom sediment of one thermokarst lake on Samoylov Island shows maximal volume 3,7 °C on 1,75 cm beneath water-sediment border [Skorospekhova, 2015]. It is also can be interpreted as biological processes activity, for example, organic material destruction with additional heating. It could be observed more detail and can be used for modeling of a lake thermic regime. Hydrobiological specificity shows similarity of species in the channels and lakes, poorness of biodiversity, especially in big channel; only stagnant in summer season Bulkurskaya channel has more zooplankton species in four times than the main river channel [Nigamatzyanova et al., 2015]. Decline of water turbidity from the delta top to channel edges is about 5-8 times [Charkin et al., 2009]. Considerable turbidity increase is formed according to permafrost thawing and can reach 500 g l-1 including high concentration of carbon and biogenic elements. Thermokarst lake degradation [Morgenstern et al., 2011] plays also an important role for permafrost hydrology in the delta. Outflow from an ice complex forms a high local suspended supply in adjacent river branches and influences on biological processes consequently [Dubinenkov et al., 2015]. Underestimated effect of water and sediment discharge increase in the middle part of river branches had been marked [Fedorova et al., 2015]. Head flux of the large Lena River forms taliks under channels with more sophisticated affect in the shoreline zone of the Laptev Sea due to aquifer dynamic and mixing of fresh and salt water. Talik effect on hydrology and sedimentation (and suspended material transformation) in the central part of the delta is currently carried out according to geophysical and hydrogeological methods. First field measurements are planned to be done in April 2016 and results will be presented in the ICOP 2016. The studies have been done with support of RFBR grant 14-05-00787 and 15-35-50949, in the framework of Russian-German projects “ CarboPerm” and “Scientific station “Samoylov Island”. The project for both SPBU and DFG funding had also applied for field and scientific investigation as well. References Bobrova, O.; Fedorova, I.; Chetverova, A.; Runkle, B. and Potapova, T. Input of Dissolved Organic Carbon for Typical Lakes in Tundra Based on Field Data of the Expedition Lena–2012. In Proceedings of the 19th International Northern Research Basins Symposium and Workshop, Southcentral Alaska, USA – August 11–17, 2013, 2013. Charkin, A.N.; Dudarev, O.V.; Semiletov, I.P.; Fedorova, I.; Chetverova, A.A.; J., Vonk; Sanchez- Garcia, L.; Gustafsson, ö. and Andersson, P. edimentation in the System of the Delta Lena River - the South Western Part of Buor-Haya Gulf (the Laptev Sea). In The 16th International Symposium on Polar Sciences. Incheon, Korea. 2009, 2009. Dubinenkov, I.; Flerus, R.; Schmitt-Kopplin, P.; Kattner, G. and Koch, B.P. [2015]: Origin-specific molecular signatures of dissolved organic matter in the Lena Delta. Biogeochemistry, 123(1):1–14, doi:10.1007/s10533-014-0049-0. Fedorova, I.; Chetverova, A.; Bolshiyanov, D.; Makarov, A.; Boike, J.; Heim, B.; Morgenstern, A.; Overduin, P. P.; Wegner, C.; Kashina, V.; Eulenburg, A.; Dobrotina, E. and Sidorina, I. [2015]: Lena delta hydrology and geochemistry: long-term hydrological data and recent field observations. Biogeosciences, 12(2):345–363, doi:10.5194/bg-12-345-2015. Morgenstern, A.; Grosse, G.; Günther, F.; Fedorova, I. and Schirrmeister, L. [2011]: Spatial analyses of thermokarst lakes and basins in Yedoma landscapes of the Lena Delta. The Cryosphere, 5(4):849–867, doi:10.5194/tc-5-849-2011. Nigamatzyanova, G.; Frolova, L.; Chetverova, A. and Fedorova, I. Hydrobiological investigation of branches of the Lena River edge zone. In Uchenye Zapiski Kazanskogo Universiteta, Seriya Estestvennye Nauki. 2015. in Russian. Skorospekhova, T. Report of a spring campaign of the expedition “Lena 2015”. AARI’s library stock, 2015.

Description: Thermo-erosional landforms (valleys, gullies) and their associated streams are the main connecting pathways between inland permafrost areas and rivers and coasts. Surface and ground waters are routed along these streams, which transport particulate and dissolved matter from the catchments to the rivers and coastal waters. Regions of ice-rich permafrost, such as the Yedoma-type Ice Complex, are not only characterized by a high abundance of thermo-erosional landforms, which formed during the Holocene, but are subject to extensive degradation under current arctic warming by processes such as thermal erosion, thermokarst, and active layer deepening. In the Siberian Lena River Delta Yedoma-type Ice Complex deposits occur on insular remnants of a Late-Pleistocene accumulation plain that has been dissected by Lena River branches and degraded by thermal erosion and thermokarst during the Holocene. This region serves as suitable exemplary study area for estimating the contribution of 1) different permafrost degradation landforms to the export of water and dissolved matter from Yedoma-type Ice Complex to the river and 2) active degradation of old permafrost versus seasonal runoff from the surface and active layer. In the summers of 2013 and 2014 we sampled surface and soil waters from streams and their watersheds in Yedomatype Ice Complex landscapes of the Lena River Delta and analyzed them for a range of hydrogeochemical parameters including electrical conductivity (EC), dissolved organic carbon (DOC) and stable isotopic composition. The sampling sites were spread over an E-W-extent of about 150 km and are characterized by very diverse geomorphological and hydrological situations in terms of distance to the river branches, catchment size, discharge, degree of thermo-erosional activity, and connection to other permafrost degradation landforms (thermokarst lakes and basins). Three key sites were sampled three and four times from June to September 2013 and 2014, respectively, in order to analyze intra-seasonal changes. The results show large variances in EC (25 to 1205 μS/cm), DOC concentrations (2.9 to 119.0 mg/l), �18O (-29.8 to -14.6 ‰ vs. SMOW), and �D (-228.9 to -117.9‰ vs. SMOW) over the whole dataset, with distinct characteristics in the parameter combination for different degradation landform and water types. The temporal variability at the repeatedly sampled sites is low, which implies that there is not much change in the processes that determine the water composition throughout the summer season. By comparing differences in surface water chemistry between flow path systems that tap into varying amounts of source water (precipitation, surface and ground water, ground ice) and have differing residence times and extents, we explore the effect of future changes in thermokarst and thermo-erosional intensity and resulting changes in flow path hydrogeochemistry for thermoerosional features draining ice-rich permafrost.